The use of polyolefin flexible foams with typical thicknesses between 1 and 3 mm
produced by a physical foaming extrusion process is nowadays quite widespread in the
packaging sector. Their high flexibility and closed-cell structure allows them to show good
energy absorption properties under low loading conditions. Although the compressive response
of these materials is well known, the inner microstructure developed during processing induce
a high anisotropy that is responsible for their direction-dependent tensile and fracture
behaviours. In this work, two different polyolefin-based foams, with densities ranging from 20
to 45 kg/m3, were studied. The induced microstructure anisotropy was characterized by micro-
Raman. With this technique, the relative orientations of both crystalline and amorphous phases
in the foam’s base polymer could be determined and thus related to their mechanical properties
measured in the different directions.